The present invention relates to a method for placement of therapeutic agents so as to reduce unwanted cellular adhesions. Unwanted cellular adhesions may include, but are not restricted to, adhesions between tumor cells and other tumor cells, adhesions between tumor cells and normal cells, and certain adhesions between normal cells and other normal cells.
Tumor cells are found in two distinct modes: as ascites (free floating cells) and as solid tumors (attached/adhered to host tissue/organs as well as to other tumor cells). Prevention of tumor cell adhesion and growth is a major clinical problem. The control of local tumor recurrence after surgical removal of malignancies is an especially serious concern. The observation that tumor growth occurs at the incision site, even at histopathologically "clean" margins, has led to the conclusion that viable tumor cells have higher affinity for damaged tissue than for normal tissue. This represents one particularly critical aspect of a much broader issue concerning prevention and control of unwanted cellular adhesions. For instance, in cases involving surgical intervention in the abdominal cavity for conditions such as inflammatory bowel disease or endometriosis, there is often the complication of postsurgical adhesions of normal tissue to the resected areas, in a manner similar to that of tumor cell adhesion and colonization or invasion of the wound.
In addition to clinical observations, experimental models of tumor cell adhesion have likewise demonstrated that damaged tissue is an attractive site for tumor growth after systemic injection of viable tumor cells. See, for example, S. Murthy and E. Scanlon, eds., Injury and Tumor Implantation: Biological Mechanisms and Clinical Implications for Recurrence and Metastasis. R.G. Landes Co., Austin, Tex. 1993. It has been reported that specific adhesion molecules and their recognition molecules (receptors) play a role between tumor cell and endothelial cells or extracellular matrix attachment. B. Zetter, Seminars in Cancer Biology, 4: 219-229 (1993). There is a growing list of families of adhesion molecules which are expressed by tumor cells and are stimulated by various environmental conditions or factors, e.g., cytokines.
More recently, there has been a report of evidence showing that display of the receptors or adhesion molecules requires intracellular components known as cytoskeletal elements. F. Pavalko and C. Otey, Proc. Society Exp. Biol. Med., 205: 282-293 (1994); D. Tang, et al., Cancer Res. 54:1119-1129 (1994).
The cytoskeleton is composed of microtubules and various filaments of self-assembling polymers of proteins including tubulin, vimentin, and actin. Adhesion molecules allow communication between the cytoplasmic domains and the cytoskeleton triggering a variety of cellular functions including cell-cell interactions, cell motility and receptor-ligand interactions and receptor internalization. See F. pavalko and C. Otey, supra. Thus, agents which interfere with or disrupt the assembly of microtubules or microfilaments can prevent or inhibit the expression of specific adhesion molecules on cells thereby blocking their recognition, binding, attachment and migration into wounded and healing, or normal tissue.
Colchicine is an agent which binds to tubulin and causes depolymerization of microtubules. Treatment of tumor cells with colchicine has been shown to decrease their ability to bind to lymphatic tissue. See, for example, S. Islam et al., Surgery 113: 676-82 (1993). Treatment of endothelial cells with colchicine likewise blocked tumor cell binding to specific adhesion molecules, as reported by D. Tang, et al., supra. Therefore, microtubule disrupting agents, which are often used in combination regimens for cancer therapy may act not only as cytostatic agents but also as anti-adhesives and possibly as anti-migratory agents thereby decreasing tumor dissemination and metastatic spread.
It has been proposed to reduce the occurrence of adhesion formation resulting from chemotherapeutic treatments involving cisplatin and bleomycin by administering these chemotherapeutic agents in combination with a vinca alkaloid substance, such as vindesine. R. Molloy et al., Irish J. Med. Sci., 159 (6): 175-77 (1990). However, no technique is provided for site specific delivery of the proposed chemotherapeutic combination.
Another approach to controlling unwanted cellular adhesions has been the use of physical barriers, including both mechanical and viscous solutions. See, for example, U.S. Pat. No. 5,250,516. Such barriers tend to prevent adhesion formation by limiting tissue apposition during the critical stages of mesothelial repair. Although use of physical barriers for preventing adhesion formation has been reasonably extensive, general acceptance is constrained because of technical difficulties.
In co-pending U.S. patent application Ser. No. 884,432, which is commonly owned with the present application, there are described various conjugates comprising a therapeutic agent or drug and a lipophilic cell binding agent, in the form of cyanine dyes substituted with relatively long hydrocarbon "tails". These conjugates are capable of stably binding to the lipid regions of cell membranes, thus enabling site selective delivery of therapeutic agents, either via local in vivo administration, e.g., by injection, or by means of a carrier, for retention at the disease site.
The above-noted conjugates afford a number of distinct advantages, as compared with compositions and methods currently available for delivery of therapeutic agents to disease sites. Most notably, the above-mentioned conjugates can be delivered and retained at a selected site in the body by stable association with cell structures at that site. Existing modes of delivery either are unable to deliver sufficient dosages to the disease site without adverse systemic side effects, or are unable to allow sufficient retention of the therapeutic agent at the disease site for a time and in an amount sufficient to produce the desired therapeutic effect.
Moreover, since the lipid regions comprise the majority of the outer membrane of the cell, it is possible to place larger numbers of lipid binding conjugates, and thus a greater concentration of therapeutic agent, into the plasma membrane. Furthermore, because the above-mentioned conjugates are stably incorporated into membrane lipids due to their hydrophobic tails, they are effectively trapped there and cannot dissociate easily. Consequently, leakage from the cells is minimized, thereby reducing undesired systemic effects.
Ongoing research involving the above-mentioned conjugates has led to the discovery of a solution to the problem of reducing unwanted cellular adhesion. When appropriately constituted and utilized, these conjugates can effectively reduce unwanted adhesions, such as: tumor cells to surgical wounds, tumor cells to normal tissue, tumor cells to tumor cells, normal cells to normal cells as in the case of surgical adhesion.